1. Field of the Invention
The present invention relates to an ink jet recording apparatus for use in recording and printing a character and image, particularly to an ink jet recording apparatus for use in a copying machine, a facsimile machine, an image output machine of a computer, or a printer.
Above all, the present invention relates to an ink supply apparatus to an ink jet head for printing/recording an image, and an ink supply mechanism provided with an ink jet head cleaning and recovering function for pressurizing and supplying an ink during cleaning and recovering of the ink jet head.
2. Related Background Art
A principle of an ink jet print system is disclosed in U.S. Pat. No. 4,723,129. As a printer, an on-demand system product has broadly spread since around 1985.
In a conventional method of supplying ink to an ink jet head of an ink jet printer, a negative pressure system has generally been used. In many cases, the ink jet head consumes ink with which a sponge or another porous material is impregnated. This form is described, for example, in Japanese Patent Application Laid-Open No. 5-270001.
In this method of supplying the ink to the ink jet head, as the ink is consumed, a negative pressure of the sponge increases, and a discharge state of an ink droplet from the ink jet head fluctuates.
In recent years, particularly to record a photographic image, a size of the ink jet droplet has been of the order of 4 to 8 pl (1 p1=1xc3x9710xe2x88x9212 liters), and an influence of the negative pressure has increased.
Moreover, a printing speed of the ink jet printer has increased because of rapid enhancement of a processing speed of an arithmetic operation element inside a computer and printer, and ink consumption has increased. Therefore, an ink supply amount from the sponge is insufficient, the negative pressure temporarily rapidly increases, and image turbulence occurs in accordance with a printing pattern. In order to solve a negative pressure fluctuation, instead of holding the ink in the sponge, the ink is held and supplied in a liquid state so that this problem can be solved. For this, a technique is disclosed, for example, in Japanese Patent Application Laid-Open No. 5-305713.
However, when printing is continuously performed with the ink jet head, dust and foreign particle stick to a surface of the ink jet head as an ink droplet discharge surface, or a slight bubble is generated inside the ink jet head. In this case, it becomes impossible to effectively discharge ink jet droplets via about 300 to 8000 ink jet discharge holes without any defect. Therefore, it is necessary to subject the ink jet head to cleaning and recovery processing after a given number of sheets are printed, or when an image defect is detected by some means. As disclosed in Japanese Patent Application Laid-Open No. 5-008401, this cleaning is performed by scraping dust off the surface of the head with a rubber plate, or by covering the surface with a cap to perform suction recovery. However, when the surface of the ink jet head held in a negative pressure state is wiped with a wiper or another plate, the rubber and foreign particle sticking to the head surface enters the ink jet discharge holes, and a problem occurs that the ink jet discharge holes are closed.
To solve the problem, a method of simultaneously performing suction and surface wiping is necessary.
However, when an apparatus is provided with both a suction mechanism and a surface wiping mechanism, the apparatus is enlarged in size, which is economically disadvantageous in respect of an apparatus manufacturing cost.
Generally considering the aforementioned conventional art problem, an ink supply apparatus and ink supply method in which a constant negative pressure is held during printing in the ink jet head, and cleaning and recovering of the ink jet head can be performed by supplying the ink in a pressurized state and discharging the ink via the ink jet head, and which is simple and small-sized and can be stable in operation have not been technically established yet.
This method is solved to some extent by a method described in Japanese Patent Application Laid-Open Nos. 10-217509 and 10-217510. This technique includes a step of supplying the ink to the ink jet head from an ink tank via ink pressurizing supply means. For a detail constitution, as shown in FIGS. 9A and 9B, ink pressurizing supply means 201 is driven by a part of a driving mechanism 804 disposed on a printer main body (not shown) side. When an ink tank 200 is mounted as shown by a dashed line of FIG. 9A, a diaphragm 804a cam-driven by the driving mechanism 804 is pushed into the ink tank 200 to pressurize an ink storage chamber. Thereby, the ink in the ink storage chamber is supplied under pressure to the ink jet head (not shown) on the printer main body side via a connection port 110.
A vale which opens to atmosphere at a constant or lower negative pressure is disposed inside the ink tank 200 in such a manner that the ink is supplied.
In this method, however, in order to supply the ink from the ink tank, a combination of two mechanisms is necessary: a mechanical operation mechanism 803, disposed inside the ink tank 200, for applying an ink supplying pressure; and the large-sized mechanism 804 disposed on the printer main body side. There is a problem that a complicated apparatus mechanism is necessary for pressurizing and supplying the ink.
As described above, the conventional example has a problem that the apparatus is enlarged in size and complicated in constitution, but in order to supply the pressurized ink to the ink jet head, some ink supply apparatus needs to be added.
Then, the present inventor has studied manufacturing of a small-sized ink supply apparatus, disposed in an outlet of a flexible ink storage baglike member, or midway in an ink supply path, for supplying the ink to the ink jet head, but have found that it is very difficult to manufacture the small-sized ink supply apparatus.
The reason is as follows. In order to print a colored photographic image, the ink jet printer requires at least four colors (black, yellow, magenta, cyan) of ink and/or light colors (light yellow, light magenta, light cyan) of ink or a flesh color of ink. When the ink tank for storing these types of ink, mechanism for pressurizing and supplying these types of ink, and ink jet head as a mechanism for receiving supply of these types of ink are mounted, the ink jet printer is necessarily enlarged, and power consumption also increases. Therefore, the size of the small-sized ink supply apparatus for pressurizing the ink needs to be small. A volumetric size of the apparatus is preferably 8 cm3 or less, power consumption needs to be one watt or less, and further an independent control operation is necessary. These problems need to be solved.
An object of the present invention is to solve the aforementioned problem, to provide a liquid pressurizing supply apparatus which is disposed in an outlet of a flexible ink storage bag-like member or midway in an ink supply path so that ink can be supplied to an ink jet head, and which is small in size, little in power consumption and simple in mechanism, and to provide a liquid discharge recording apparatus using the liquid pressurizing supply apparatus.
In order to achieve the aforementioned object, as a result of intensive studies, the present inventor et al. have found that the ink can be pressurized and supplied by manufacturing a small-sized electromagnetic actuator, and disposing a one-way valve on the actuator. The small-sized electromagnetic actuator can operate with an operation power of about one watt or less, but a large problem has further occurred.
That is, when the actuator is small-sized with power consumption of about one watt or less, a driving distance of the actuator is about 0.8 mm or less, and an amount of ink able to be supplied with one operation is small (50 xcexcliter). Therefore, if the one-way valve is not satisfactorily shielded, ink flows in a reverse direction against pressure, and a problem is that the pressure does not rise. Therefore, a method of satisfactorily pressurizing and supplying the ink even with a small driving distance and insufficient supply ability has been reviewed in more detail. As a result, the following method of solving the problem has been found.
The ink supply ability is insufficient, and the ink cannot be pressurized, because an ink reverse flow amount is large. It has been found that the amount may excessively be reduced, or set to xe2x80x9c0xe2x80x9d. As a result of checking a shielded portion of the one-way valve inside the small-sized actuator in detail, a processing scratch with a depth of 10 xcexcm or less is found, and the ink flows in the reverse direction through a gap of the scratch. To solve the problem, it has been proposed to mirror-surface abrade the corresponding surface, but it is economically impossible to use such method in manufacturing the actuator. Then, as a result of further intensive study, the problem has been solved by satisfactorily smoothening the surface of the shielded portion of the one-way valve. Moreover, an economical problem that the number of members and the number of assembly steps increase has been solved by appropriately forming components integrally with one another.
Furthermore, to enhance the ink supply ability, the actuator is provided with one check valve or a plurality of check valves. Additionally, the supply ability has further been enhanced by disposing an ink flow-in taper inside the actuator.
When the liquid pressurizing supply apparatus using the small-sized electromagnetic actuator manufactured as described above is operated in response to an ink request signal from the ink jet head, the ink can be pressurized and supplied to the ink jet head, and the aforementioned problem can be solved.
The liquid pressurizing supply apparatus of the present invention achieved to solve the various problems is constituted as follows.
That is, according to the present invention, there is provided a liquid pressurizing supply apparatus driven in response to an alternating or pulse electric signal, comprising: a high-permeability driving shaft; urging force generation means for urging the driving shaft in one direction; a bobbin case in which the driving shaft is disposed in a cylindrical chamber; a winding coil wound around an outer peripheral surface of the bobbin case; a pair of high-permeability case members in which the bobbin case with the winding coil wound therearound is contained, and a containing recess portion is formed by a sheet metal drawing process; a channel portion connected to the cylindrical chamber of the bobbin case in which the driving shaft is disposed; and at least one back-flow prevention means for preventing back-flow. In this constitution, when the electric signal is applied to the winding coil, an electromagnetic force is generated, and the driving shaft moves against the urging force of the urging force generation means in the cylindrical chamber in the bobbin case. Thereby, a liquid supplied into the chamber is pressurized and supplied via the channel portion. Subsequently, when the supply of the electric signal is stopped, the driving shaft is returned to its original position by the urging force of the urging force generation means. In this case, no back flow occurs because of an action of the back-flow prevention means. Therefore, the liquid can be supplied under pressure to a downstream side from an upstream side of the present apparatus by repeating the aforementioned reciprocating movement of the driving shaft. In this constitution, the small-sized apparatus can be provided at a low manufacturing cost, and can further be driven with power consumption of about one watt or less.
Moreover, in the apparatus, a portion onto which the driving shaft is pressed by the urging force generation means is a molded smooth surface integrally molded with the bobbin case, a portion of the driving shaft bonded to the molded smooth surface is provided with a seal rubber, and the channel portion is preferably shielded by the molded smooth surface and seal rubber. Alternatively, the portion onto which the driving shaft is pressed by the urging force generation means is a coated smooth surface formed on a bottom surface of the containing recess portion of the high-permeability case member, the portion of the driving shaft bonded to the coated smooth surface is provided with the seal rubber, and the channel portion is preferably shielded by the coated smooth surface and seal rubber. In this constitution, in a standby state before driving, the seal rubber of the driving shaft is pressed onto the molded smooth surface or the coated smooth surface, and the channel portion is satisfactorily shielded. Therefore, even when the moving distance is short and the liquid supply amount is small, the liquid can satisfactorily pressurized and supplied.
For the back-flow prevention means, the apparatus is provided with one or both of a ball check valve and a film check valve. With this constitution, the back flow is satisfactorily prevented, and the liquid pressurizing supply ability is enhanced.
In the cylindrical chamber of the bobbin case, an inclined taper portion for enlarging an inner diameter in the vicinity of the portion onto which the driving shaft is pressed by the urging force generation means of the chamber is preferably formed. With this constitution, a liquid flow-in resistance decreases, and the liquid supply ability is further enhanced.
A volume of the apparatus is 8 cm3 or less, a moving distance of the driving shaft is in a range of 0.1 to 0.8 mm, and a power of the electric signal is in a range of 0.2 to 1.5 W.
Moreover, according to the present invention, there is provided a liquid discharge recording apparatus comprising: a liquid discharge head for ejecting a liquid droplet to record an image; liquid residual amount detection means; liquid storage means; a liquid supplying pipe for supplying a liquid of the liquid storage means to the liquid discharge head; one of above mentioned a liquid pressurizing supply apparatuses; and driving control means of the liquid pressurizing supply apparatus. The liquid pressurizing supply apparatus is disposed midway in the liquid supplying pipe or in a liquid guide outlet of the liquid storage means. The driving control means allows the liquid pressurizing supply apparatus to supply the liquid in a pressurized state during cleaning/recovering of the liquid discharge head so that the liquid is ejected via a discharge orifice of the liquid discharge head. In this constitution, during cleaning/recovering of the liquid discharge head, the liquid is ejected via the discharge orifice of the liquid discharge head, while a surface with the discharge orifice formed therein can be wiped with a wiper. Therefore, dust, and the like on the surface with the discharge orifice formed therein are prevented from being pushed into the discharge orifice.
The liquid storage means can be applied in normal pressure, 0-pressure, or negative pressure state of a head pressure of 0 to 1000 mm aq.
The liquid discharge recording apparatus is preferably disposed for each color system.